Bottom line: for some applications an Altoid tin is perfectly adequate, for other applications, not so much. Anyone can see at a glance they'd be useless if dunked in water.

I use an Altoids for keeping some small items in a form that's easier to not get misplaced. My EDC items are pocket carry. No Altoid tin means no tin to leak

OTOH a small bit of tape used in the right places and a ranger band can do wonders for keeping wet stuff out.